Characterization of interface structures and morphologies of heterogeneous polymers: A solid-state exp 1 H NMR study

Industrial polymers for the most part are composites of two or more polymers with heterogeneous phases at submicrometer range. The domain sizes of each component, as well as interface structures, dictate the ultimate properties and applications of these polymers, such as impact strength and melt properties. The solid-state NMR spin diffusion technique has been employed to study polymer morphologies with a unique emphasis on interface structures. The use of exp 1 H detected experiments has been shown to provide high sensitivity for a fraction of the time needed to acquire the signal compared to the widely used exp 13 C detection experiments of rigid and mobile polymer components. Twice as much interface thickness was obtained from exp 1 H detected experiments as compared to exp 13 C detected data for diblock polymers. A series of dipolar filter experiments are used to obtain a more accurate quantitative ratio of the rigid, interface, and mobile components of a binary polymer with limited or no long-range order. As a result, this approach is an excellent method for comparing similar composite materials for interface structures. This approach is not limited to regular morphologies, and no structural model is needed to interpret the data and obtain quantitative information. In addition, the nature of the interface gradient from the rigid phase to the mobile phase is uniquely studied by this approach. (Example material: polystyrene-polybutadiene block copolymers.)